Compressors are used in refrigeration systems, environment control systems, air conditioning systems and the like. For convenience, the invention will be described with particular reference to air conditioning systems. Air conditioning systems utilize compressors of varying sizes ranging from very small compressors used in motor vehicles and domestic situations to compressors of up to thousands of Tons capacity used in commercial air-conditioning equipment.
Refrigerants and air conditioning systems currently use a refrigerant R12 or a singular refrigerant that is a CFC or HCFC refrigerant, which is now known as potentially damaging to the environment, or R22, which is currently approved for use under the Montreal Protocol on the ozone layer until 2030 A.D for example. However, use of any refrigerant must be in progressively reduced volumes. A main CFC-free commercial refrigerant currently endorsed without reservation by the Montreal Protocol and by the International Heating, Ventilation and Air Conditioning Industry (HVAC) is the refrigerant known as R134A. This refrigerant, however, is commercially unsuitable as a direct replacement for the CFC refrigerants in existing hematic or semi-hematic machines because the chemical structure of R134A results in a performance loss of up to 30%. Furthermore, the refrigerant R134A is basically unsuitable for use with existing compressors without major mechanical changes because the refrigerant is chemically incompatible with lubricants now available for mechanical bearings and other rotating or reciprocating pans of the compressors.
Another difficulty with current air conditioning systems is that, traditionally, small to medium refrigeration systems of a capacity in the range between 1 and 150 kilowatts use reciprocating, rotary or scroll compressors, which are relatively cheap to produce but are also relatively inefficient. Screw compressors become more efficient at sizes between 50 and 300 Tons although most systems over 180 Tons use centrifugal compressors, since these are more efficient than screw compressors. However, centrifugal compressors, which, basically, comprise a rotor sending air radially outwards into a stator under centrifugal action to create compression, involve high rotational speeds and are generally far more costly to produce and maintain.
In summary, the efficiency of the smaller equipment below 180 Tons is restricted by the available technology in the reciprocating, rotary, scroll and screw compressors. While centrifugal machines can offer a higher efficiency in the lower capacity range, limitations on high rotational speed drives, and the cost thereof, inhibits their use.